Mechanical energy harvesting is an increasingly important method of providing power. This power can be used for a variety of tasks, including providing power to distributed sensor networks where physical connection to a power source is impractical. Conventional mechanical energy harvesting methods rely on piezoelectric, electromagnetic, or electrostatic conversion of mechanical energy from ambient vibration sources to electrical energy. However, the low energy density of these devices excludes their application in low frequency and static load sources, with the lowest frequency reported devices limited to 10 Hz.
For example, a 50 MPa mechanical load source at 0.01 Hz could be used in sensor applications with a device capable of harvesting 10−2 J/cm3 per cycle. However, the device would require an energy density of 10−1 J/cm3 per cycle to be viable for mobile electronics applications. These applications are determined by comparing average power densities characteristic of each application based on energy density of a battery divided by application run time; this method eliminates the need to make assumptions about the acceptable size of the power source required for an application.
A way to overcome these limitations, to provide a device capable of use in low frequency applications, is therefore desirable.